Measuring brain connectivity: Diffusion tensor imaging validates resting state temporal correlations

Abstract

Diffusion tensor imaging (DTI) and resting state temporal correlations (RSTC) are two leading techniques for investigating the connectivity of the human brain. They have been widely used to investigate the strength of anatomical and functional connections between distant brain regions in healthy subjects, and in clinical populations. Though they are both based on magnetic resonance imaging (MRI) they have not yet been compared directly. In this work both techniques were employed to create global connectivity matrices covering the whole brain gray matter. This allowed for direct comparisons between functional connectivity measured by RSTC with anatomical connectivity quantified using DTI tractography. We found that connectivity matrices obtained using both techniques showed significant agreement. Connectivity maps created for a priori defined anatomical regions showed significant correlation, and furthermore agreement was especially high in regions showing strong overall connectivity, such as those belonging to the default mode network. Direct comparison between functional RSTC and anatomical DTI connectivity, presented here for the first time, links two powerful approaches for investigating brain connectivity and shows their strong agreement. It provides a crucial multi-modal validation for resting state correlations as representing neuronal connectivity. The combination of both techniques presented here allows for further combining them to provide richer representation of brain connectivity both in the healthy brain and in clinical conditions.

Precuneus shares intrinsic functional architecture in humans and monkeys

“…Despite obvious differences in scale and complexity between human and macaque brains and differences in data collection between the 2 species, the RSFC relationships that we observed in vivo were largely consistent with anatomical tracing studies in the monkey, although some differences were also noted, suggesting that this emerging technique does reflect aspects of underlying anatomical connectivity. While several recent comparisons of structural and functional connectivity support a relationship between these measures (40)(41)(42), multiple factors may influence patterns of RSFC (43,44), and, as we have observed, the relationship with anatomical connectivity is not a 1:1 correspondence.…”

Modeling Causal Relationship Between Brain Regions Within the Drug-Cue Processing Network in Chronic Cocaine Smokers

“…To conclude, this study has contributed two novel findings: (1) during exposure to cocaine cues, cocaine smokers showed a feed-forward effective connectivity pattern between the ROIs of the drug-cue processing network (amygdala → hippocampus → dorsal striatum → insula → medial frontal cortex, dorsolateral prefrontal cortex, anterior cingulate cortex) that was not present when the controls viewed the cocaine cues, and (2) craving ratings among cocaine smokers were positively correlated with the strength of causal influence of insula on dorsolateral prefrontal cortex. Future research will include using both fMRI and diffusion tensor imaging techniques to look for a relationship between effective and anatomical connectivity (Skudlarski et al, 2008) between the ROIs of the drug-cue processing network in cocaine users. Another future research will examine the influence of gender on the causal relationship between the ROIs of the drug-cue processing network during cocaine-cue exposure and empirically test the theoretical model as we propose in this study.…”

MR connectomics: Principles and challenges

“…Indeed, connectionbased subdivisions of premotor cortex (Johansen-Berg et al, 2004) have been found to correspond closely to the subdivisions identified using functional imaging of motor and linguistic tasks in the same individuals, and connection-based subdivisions of thalamus (Zhang et al, 2008) as well as inferior frontal cortex (Anwander et al, 2007) and cingulate cortices (Beckmann et al, 2009) have been found to match the canonical functional parcellations of these areas. In a less function-specific vein, other groups have investigated the relationship, across the brain, between so-called "functional connectivity" which is assessed using correlations in resting-state BOLD signal with structural connectivity identified using diffusion imaging (Greicius et al, 2009;Hagmann et al, 2008;Honey et al, 2009;Koch et al, 2002;Skudlarski et al, 2008;van den Heuvel et al, 2008van den Heuvel et al, , 2009van den Heuvel et al, 2009;Van Dijk et al, 2010). These studies are of a more exploratory nature, because the functional significance and neurophysiological basis of the correlation patterns in resting-state BOLD signal are not well understood.…”